title: Granulomatous mastitis: the histological differentials.
abstract: BACKGROUND
  The management of granulomatous mastitis depends on the causative factor, and accurate diagnosis in distinguishing between idiopathic granulomatous mastitis (IGM) and tuberculous mastitis (TBM) is indispensable. This is particularly problematic in the cases of granulomatous mastitis in which the microbiological studies are negative. In this study, in a large cohort, the histological features for IGM and TBM were compared.
  
  
  METHODS
  The histopathology files from the two participating hospitals were searched for cases of granulomatous inflammation of the breast over an 8-year period. The parameters assessed included age of patient, lesional size, systemic and local symptoms, and histological findings of inflammatory cells, granulomas, necrosis, multinucleated giant cells, fibrosis and calcifications.
  
  
  RESULTS
  29 cases of IGM and 33 cases of TBM were included in this study. A significant difference was seen between the two groups with regard to patient age (t=2.52, p<0.05) and lesional size (t=-5.56, p<0.01). TBM occurred in a significantly younger population, and demonstrated larger lesional sizes than IGM. There was no difference between the number of cases showing mass, local and systemic symptoms. Comparing the different histological features, the TBM group showed significantly more fibrosis, eosinophils and necrosis, whereas the IGM group showed significantly more plasma cells. Taking all the cases together as one group to evaluate the relationship between the histological parameters, there was significant positive correlation between eosinophils and fibrosis (r(s)=0.39, p<0.01), and negative correlation between vague and well-formed granulomas (r(s)=-0.38, p<0.01).
  
  
  CONCLUSIONS
  TBM was more likely to occur in younger patients, with a larger clinical mass at presentation. Histologically, TBM tends to show more eosinophils and necrosis, and IGM is associated with more plasma cells. The characteristics of the granulomas and giant cells were not distinguishing features.
authors.affiliation: Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Maribel
authors.initials: M
authors.lastname: Lacambra
authors.forename: Tu Anh
authors.initials: TA
authors.lastname: Thai
authors.forename: Christopher C F
authors.initials: CC
authors.lastname: Lam
authors.forename: Alex M C
authors.initials: AM
authors.lastname: Yu
authors.forename: Huong Thien
authors.initials: HT
authors.lastname: Pham
authors.forename: Phuong Viet The
authors.initials: PV
authors.lastname: Tran
authors.forename: Bonita K B
authors.initials: BK
authors.lastname: Law
authors.forename: Thanh
authors.initials: T
authors.lastname: Van Nguyen
authors.forename: Dung Xuan
authors.initials: DX
authors.lastname: Pham
authors.forename: Gary M
authors.initials: GM
authors.lastname: Tse
mesh_terms: D000328:Adult; D017677:Age Distribution; D015331:Cohort Studies; D003937:Diagnosis, Differential; D004804:Eosinophils; D005260:Female; D005355:Fibrosis / Q000473:pathology; D058890:Granulomatous Mastitis / Q000175:diagnosis*; D006801:Humans; D008413:Mastitis / Q000175:diagnosis* / Q000209:etiology / Q000382:microbiology; D008875:Middle Aged; D012189:Retrospective Studies; D014376:Tuberculosis / Q000150:complications / Q000175:diagnosis*; D055815:Young Adult